SELinux policies for Perfetto cmdline client (/system/bin/perfetto)

Instead of having statsd linking the perfetto client library
and talk directly to its socket, we let just statsd exec()
the /system/bin/perfetto cmdline client.

There are two reasons for this:
1) Simplify the interaction between statsd and perfetto, reduce
  dependencies, binary size bloat and isolate faults.
2) The cmdline client also takes care of handing the trace to
  Dropbox. This allows to expose the binder interaction surface
  to the short-lived cmdline client and avoid to grant binder
  access to the perfetto traced daemon.

This cmdline client will be used by:
 - statsd
 - the shell user (for our UI and Studio)

Bug: 70942310
Change-Id: I8cdde181481ad0a1a5cae5937ac446cedac54a1f

private/compat/26.0/26.0.ignore.cil

@@ -59,6 +59,10 @@
     network_watchlist_data_file
     network_watchlist_service
     package_native_service
+    perfetto
+    perfetto_exec
+    perfetto_tmpfs
+    perfetto_traces_data_file
     perfprofd_service
     property_info
     slice_service

private/file.te

@@ -9,3 +9,6 @@ type storaged_data_file, file_type, data_file_type, core_data_file_type;
 
 # /data/misc/wmtrace for wm traces
 type wm_trace_data_file, file_type, data_file_type, core_data_file_type;
+
+# /data/misc/perfetto-traces for perfetto traces
+type perfetto_traces_data_file, file_type, data_file_type, core_data_file_type;

private/file_contexts

@@ -246,6 +246,7 @@
 /system/bin/usbd   u:object_r:usbd_exec:s0
 /system/bin/inputflinger u:object_r:inputflinger_exec:s0
 /system/bin/logd        u:object_r:logd_exec:s0
+/system/bin/perfetto        u:object_r:perfetto_exec:s0
 /system/bin/traced        u:object_r:traced_exec:s0
 /system/bin/traced_probes        u:object_r:traced_probes_exec:s0
 /system/bin/uncrypt     u:object_r:uncrypt_exec:s0
@@ -391,6 +392,7 @@
 /data/misc/media(/.*)?          u:object_r:media_data_file:s0
 /data/misc/net(/.*)?            u:object_r:net_data_file:s0
 /data/misc/network_watchlist(/.*)? u:object_r:network_watchlist_data_file:s0
+/data/misc/perfetto-traces(/.*)? u:object_r:perfetto_traces_data_file:s0
 /data/misc/recovery(/.*)?       u:object_r:recovery_data_file:s0
 /data/misc/shared_relro(/.*)?   u:object_r:shared_relro_file:s0
 /data/misc/sms(/.*)?            u:object_r:radio_data_file:s0

private/perfetto.te

@@ -0,0 +1,60 @@
+# Perfetto command-line client. Can be used only from the domains that are
+# explicitly whitelisted with a domain_auto_trans(X, perfetto_exec, perfetto).
+# This command line client accesses the privileged socket of the traced
+# daemon.
+
+type perfetto, domain, coredomain;
+type perfetto_exec, exec_type, file_type;
+
+tmpfs_domain(perfetto);
+
+# Allow to access traced's privileged consumer socket.
+unix_socket_connect(perfetto, traced_consumer, traced)
+
+# Allow to write and unlink traces into /data/misc/perfetto-traces.
+allow perfetto perfetto_traces_data_file:dir rw_dir_perms;
+allow perfetto perfetto_traces_data_file:file create_file_perms;
+
+# Allow to access binder to pass the traces to Dropbox.
+binder_use(perfetto)
+binder_call(perfetto, system_server)
+allow perfetto dropbox_service:service_manager find;
+
+# Allow statsd and shell to pipe the trace config to perfetto on stdin and to
+# print out on stdout/stderr.
+allow perfetto statsd:fd use;
+allow perfetto statsd:fifo_file { getattr read write };
+allow perfetto shell:fd use;
+allow perfetto shell:fifo_file { getattr read write };
+
+# Allow to communicate use, read and write over the adb connection.
+allow perfetto adbd:fd use;
+allow perfetto adbd:unix_stream_socket { read write };
+
+# allow adbd to reap perfetto
+allow perfetto adbd:process { sigchld };
+
+# Allow to access /dev/pts when launched in an adb shell.
+allow perfetto devpts:chr_file rw_file_perms;
+
+###
+### Neverallow rules
+###
+### perfetto should NEVER do any of this
+
+# Disallow mapping executable memory (execstack and exec are already disallowed
+# globally in domain.te).
+neverallow perfetto self:process execmem;
+
+# Block device access.
+neverallow perfetto dev_type:blk_file { read write };
+
+# ptrace any other process
+neverallow perfetto domain:process ptrace;
+
+# Disallows access to other /data files.
+neverallow perfetto { data_file_type -system_data_file -zoneinfo_data_file -perfetto_traces_data_file }:dir *;
+neverallow perfetto { system_data_file -perfetto_traces_data_file }:dir ~{ getattr search };
+neverallow perfetto zoneinfo_data_file:dir ~r_dir_perms;
+neverallow perfetto { data_file_type -zoneinfo_data_file -perfetto_traces_data_file }:lnk_file *;
+neverallow perfetto { data_file_type -zoneinfo_data_file -perfetto_traces_data_file }:file ~write;

private/shell.te

@@ -38,3 +38,12 @@ allow shell traced_tmpfs:file { read write getattr map };
 unix_socket_connect(shell, traced_producer, traced)
 
 domain_auto_trans(shell, vendor_shell_exec, vendor_shell)
+
+# Allow shell binaries to exec the perfetto cmdline util and have that
+# transition into its own domain, so that it behaves consistently to
+# when exec()-d by statsd.
+domain_auto_trans(shell, perfetto_exec, perfetto)
+
+# Allow shell to read and unlink traces stored in /data/misc/perfetto-traces.
+allow shell perfetto_traces_data_file:dir rw_dir_perms;
+allow shell perfetto_traces_data_file:file r_file_perms;

private/statsd.te

@@ -37,8 +37,11 @@ binder_call(statsd, system_server)
 read_logd(statsd)
 control_logd(statsd)
 
-# Allow to control Perfetto traced and consume its traces.
-unix_socket_connect(statsd, traced_consumer, traced)
+# Allow to exec the perfetto cmdline client and pass it the trace config on
+# stdint through a pipe. It allows statsd to  capture traces and hand them
+# to Android dropbox.
+allow statsd perfetto_exec:file rx_file_perms;
+domain_auto_trans(statsd, perfetto_exec, perfetto)
 
 # Grant statsd with permissions to register the services.
 allow statsd {

private/su.te

@@ -13,6 +13,9 @@ userdebug_or_eng(`
   # Put the incident command into its domain so it is the same on user, userdebug and eng.
   domain_auto_trans(su, incident_exec, incident)
 
+  # Put the perfetto command into its domain so it is the same on user, userdebug and eng.
+  domain_auto_trans(su, perfetto_exec, perfetto)
+
   # su is also permissive to permit setenforce.
   permissive su;
 

private/system_server.te

@@ -371,6 +371,11 @@ allow system_server dumpstate:fifo_file append;
 # with no DAC access to it, for dropbox to read.
 allow system_server incident_data_file:file read;
 
+# Allow dropbox to read /data/misc/perfetto-traces. Only the fd is sent over
+# binder.
+allow system_server perfetto_traces_data_file:file read;
+allow system_server perfetto:fd use;
+
 # Manage /data/backup.
 allow system_server backup_data_file:dir create_dir_perms;
 allow system_server backup_data_file:file create_file_perms;
@@ -821,4 +826,3 @@ neverallow system_server { domain -system_server }:process ptrace;
 # CAP_SYS_RESOURCE was traditionally needed for sensitive /proc/PID
 # file read access. However, that is now unnecessary (b/34951864)
 neverallow system_server system_server:global_capability_class_set sys_resource;
-